The invention relates generally to the field of transport refrigeration systems. More specifically, the invention relates to methods and systems that provide auxiliary electric power from a truck trailer refrigeration unit depending on refrigeration demand.
Transport refrigeration systems such as those used on truck trailers, typically employ a mechanically coupled shaft driven compressor or an electric motor driven compressor. In the mechanical scheme, an engine such as a diesel is either directly or indirectly coupled to the refrigeration compressor. The engine may also drive the refrigeration condenser fans, evaporator fans, and other components through additional mechanical drives using pulleys, V-belts and the like.
For mechanical refrigeration systems, electric power is limited. Usually, the only available power is 12 VDC that is available from the refrigeration system engine battery. This low voltage may be used to supply power for lighting within a trailer box or for a lift gate mechanism.
In the electrical scheme, the engine is coupled to a generator or alternator of the refrigeration system which provides electric power for all refrigeration loads. Refrigeration loads typically include a compressor motor, condenser fan motors, evaporator fan motors, electric defrosting heaters, and other electric loads.
What is desired is a system that provides additional power for auxiliary loads.